You've already expended multiple times the effort it would have taken just to fix it. DHCP is asking you for the info it needs to create & assign addresses that fit your network. (i.e. tell it how you're building your network!)

Very basic example, my network machines used to be addressed in the 192.168.2.{nn} range ({nn} being the machine assignment on that network), so my declaration in the .conf file would look like:

subnet 192.168.2.0 netmask 255.255.255.0

If you're addressing your machines with addresses like 10.0.2.{nn}, yours might then be

subnet 10.0.2.0 netmask 255.255.255.0

or for 192.168.138.{nn} machines

subnet 192.168.138.0 netmask 255.255.255.0

As mentioned, this was just a simple example so that your DHCP will know how to address network machines that plug-in to it. I am left to wonder, given your settings, how your DHCP is working ... or maybe you're assigning fixed addresses, our your router is also running DHCP. In any case, this is a snowball that is building at the top of the hill - eventually, you'll be bumping into this (and much more) again as you progress if you just let it go. <wink>